Light controlled spatial and angular electromagnetic wave modulator

Abstract

A 2D/3D optically controlled spatial and angular electromagnetic wave modulator is disclosed. The modulator of the present invention modulates the amplitude and direction of an electromagnetic wave such as millimeter microwaves or infrared waves by diffracting or scattering the electromagnetic wave from a semiconductor material upon which is incident a controlling lightwave. The lightwave incident upon the semiconductor is of varying intensity, and may be time varying, and changes the complex refractive permittivity of the semiconductor material. The electromagnetic wave is thus modulated in accordance with the controlling lightwave.

We claim: 
     
       1. A multi-dimensional modulator for spatially modulating an electromagnetic wave with a controlling light wave, the modulator comprising: a semiconductor material having an absorption band;   a first source of light having a wavelength spectrum located within the absorption band of said semiconductor material;   means for spatially modulating said light with information in the form of a 2-D pattern to generate said controlling light wave;   means for delivering said controlling light wave onto the surface and into the volume of said semiconductor material, said controlling light wave generating a 2-D distribution of the complex permitivity of said semiconductor material which follows the pattern of said controlling light wave;   a second source of said electromagnetic wave, said second source having a different wavelength spectrum than said first source and outside said absorption band, said second source arranged so that said electromagnetic wave is incident upon said semiconductor material and is directly spatially modulated in accordance with the changing complex permitivity of said semiconductor material generated by said controlling light wave.   
     
     
       2. The invention as defined in claim 1 further characterized in that the electromagnetic wave is reflected from said semiconductor material. 
     
     
       3. The invention as defined in claim 1 further characterized in that the electromagnetic wave is transmitted through said semiconductor material. 
     
     
       4. The invention as defined in claim 1 wherein said material is thin so that the variation in complex permitivity is substantially in two dimensions. 
     
     
       5. The invention as defined in claim 1 wherein said semiconductor material is thick so that the variation in complex permitivity is in three dimensions. 
     
     
       6. The invention as defined in claim 1 wherein the lightwave is in the range visible to near IR. 
     
     
       7. The invention as defined in claim 1 wherein the electromagnetic wave is substantially in the range 1-100 μm. 
     
     
       8. The invention as defined in claim 1 further characterized in that the complex permitivity of said semiconductor material is periodic and varies with time. 
     
     
       9. The invention as defined in claim 1 wherein the light incident upon said semiconductor material creates a holographic interference pattern so that outgoing electromagnetic waves form a 3-dimensional holographic image. 
     
     
       10. A multi-dimensional modulator for spatially modulating an electromagnetic wave with a controlling light wave, the modulator comprising: a semiconductor material having an absorption band;   a first source of light having a wavelength spectrum located within the absorption band of said semiconductor material;   means for spatially modulating said light with information in the form of a 2-D pattern to generate said controlling light wave;   means for delivering said controlling light wave onto the surface and into the volume of said semiconductor material, said controlling light wave generating a 2-D distribution of the complex permitivity of said semiconductor material which follows the pattern of said controlling light wave;   a second source of said electromagnetic wave, said second source arranged so that said electromagnetic wave is incident upon aid semiconductor material and is directly spatially modulated in accordance with the changing complex permitivity of said semiconductor material generated by said controlling light wave, said electromagnetic wave being substantially in the range 1 mm-1 cm.   
     
     
       11. A continuously distributed light controlled antenna employing a controlling light wave and providing 2-dimensional control of an electromagnetic wave, the antenna comprising: a semiconductor material having an absorption band;   a first source of light having a wavelength spectrum located within the absorption band of said semiconductor material;   means for spatially modulating said light with information in the form of a 2-D pattern to generate a controlling light wave;   means for delivering said controlling light wave onto the surface and into the volume of said semiconductor material, said controlling light wave generating a 2-D distribution of the complex permitivity of said semiconductor material which follows the pattern of said controlling light wave;   a second source of said electromagnetic wave, said second source having a different wavelength spectrum than said first source and outside said absorption band, said second source arranged so that said electromagnetic wave is incident upon said semiconductor material and is directly spatially modulated in accordance with the changing complex permitivity of said semiconductor material generated by said controlling light wave.   
     
     
       12. An infrared light modulator for spatially modulating an electromagnetic wave with a controlling time variable infrared wave, the modulator comprising: a semiconductor material having an absorption band and sides polished to optical quality;   a first source of said infrared wave;   means for spatially modulating said infrared wave with information in the form of a 2-D pattern to generate a controlling light wave;   mans for delivering the controlling light wave onto the surface and into the volume of said semiconductor material, said controlling light wave generating a time variable spatial modulation of the complex permitivity of said semiconductor material in direct response to the intensity of said infrared wave;   a second non-infrared source of said electromagnetic wave, said second source arranged so that said electromagnetic wave is incident upon and reflected from said semiconductor material and time variable spatial variations of destructive and constructive interference of the reflected electromagnetic wave occur in accordance with the changing complex permitivity of said semiconductor material.   
     
     
       13. A multi-dimensional modulator for spatially modulating an electromagnetic wave with a controlling light wave, the modulator comprising: a semiconductor material having two sides and an absorption band;   a first source of light having a wavelength spectrum located within the absorption band of said semiconductor material;   means for spatially modulating said light with information in the form of a 2-D pattern to generate said controlling light wave;   means for delivering said controlling light wave onto one side of said semiconductor material, said controlling light wave generating a 2-D distribution of the complex permitivity of said semiconductor material which follows the pattern of said controlling light wave;   a second source of said electromagnetic wave, said second source having a different wavelength spectrum than said first source and outside said absorption band, said second source arranged so that said electromagnetic wave is incident upon the other side of said semiconductor material and is directly spatially modulated in accordance with the changing complex permitivity of said semiconductor material generated by said controlling light wave.   
     
     
       14. A continuously distributed light controlled antenna employing a controlling light wave and providing 2-dimensional scanning of an electromagnetic wave, the antenna comprising: a semiconductor material having an absorption band;   a first source of light having a wavelength spectrum located within the absorption band of said semiconductor material;   means for spatially modulating said light with information in the form of a 2-D pattern to generate said controlling light wave;   means for delivering the controlling light wave onto the surface and into the volume of said semiconductor material, said controlling light wave generating a 2-D distribution of the complex permitivity of said semiconductor material which follows the pattern of said controlling light wave;   a second source of an electromagnetic wave outside said absorption band, said second source arranged so that said electromagnetic wave defines an angle of incidence and an angle of diffraction with respect to said semiconductor material, and whereby the angle of incidence is synchronized with the 2-D time varying complex permitivity of said semiconductor material so that said second source is tracked and said angle of diffraction is constant.